The present invention relates to improvements in methods and mechanisms for forming bags from plastic film or plastic film laminates, and more particularly to improved forming of bags in a form, fill and seal process.
In a form, fill and seal machine, a continuous layer of plastic or plastic laminate is drawn down over a filler tube and shaped into a bag tube with the edges of the film brought together and joined to make the bag tube. In one form as the edges of the bag are brought together, they are joined by a reclosable continuous zipper so that the edges form the eventual bag top. The bag tube is flattened beneath the filler tube and cross-sealed at intermediate spaced locations to form the side seams of the bag. When a cross-seal is made, the bag is filled with its contents through the filler tube. Another cross-seal is then made above the contents and the completed filled bag is cut from the bag tube.
In the formation of bags, it is important that a cross seal be made which is effective and tight, and particularly in the case where foodstuffs or liquid is filled into the bag, the cross-seal must be leak-proof and inasmuch as the bag tube must be pressed flat before sealing, the presence of wrinkles frequently prevents the completion of a strong seal and will result in leaks being present. The presence of wrinkles will also tend to detract from the appearance of the bag and is undesirable.